1. Field of the Invention
This invention relates to a process and a composition for treating leafy produce through the application of a preservative aqueous solution to said leafy produce thereby extending the period of freshness before discoloration and wilting occurs.
The produce industry, being quite aware of the problems associated with discoloration, wilting and other symptoms of spoilage, has attempted to maintain a fresh, appealing appearance of produce as long as possible. It is well known that leafy produce, such as spinach, lettuce, chard, and the like, suffer from such spoilage after even relatively short periods of storage. Consequently, the produce-treating industry is constantly faced with unnecessarily high costs due to spoiling of produce.
The various methods which have been proposed to overcome the spoilage problem of non-leafy produce have been primarily directed to the improvement of the color of the produce, rather than maintaining freshness through application of a preservative. These methods that are used are generally designed to bleach the produce and provide a color additive. A number of these prior art methods are somewhat limited in that they have involved the use of acids and other strong chemicals which have a tendency to injure the material being treated or require very careful, critical control of the process to avoid damage to the produce.
The conventional bleaching methods used in the treatment of produce are designed to remove various stains present on the outer skin and to generally lighten the color of the produce to make it more appealing for sale. Many of these previously proposed bleaching methods, especially those involving the use of acid solutions, also tend to char or cause an undesirable reaction between the organic material and the acid constituent of the solution. Consequently, these prior art methods are often not applicable to the treatment of many types of produce and do not materially aid in extending the fresh life.
The use of oxidizing or reducing agents and providing certain color additives or to selectively bleach the produce is generally known in the art. Such oxidizing agents include hydrogen peroxide, sulfur dioxide and sodium-sulfo-paratoluene chloramine. Examples of reducing agents which may be used include copper sulfate, ferrous sulfate, ferrous sulfite, hydrogen sulfide, titaneous chloride and stannous chloride. Sodium hypochlorite is another popular oxidizing agent frequently used in prior art produce treatment processes. This compound is generally used in solutions of sufficient concentrations to cause a bleaching action to occur when the solution is applied to the produce being treated.
2. Description of the Background Art
Prior art methods designed for the bleaching of produce utilize sodium hypochlorite as well as other additives such as hydrogen peroxide, as disclosed in U.S. Pat. No. 2,092,090 to J. N. Sharma and U.S. Pat. No. 2,155,923 to J. A. Armstrong. As disclosed in these two patents, the concentration of sodium hypochlorite, or its equivalent oxidizing agent, is used only in concentrations sufficient to produce a bleaching action on the outer skins of fruits and vegetables. Sodium hypochlorite is not used as a preservative in these prior art methods.
A process employing chlorites for bleaching non-cellulosic organic materials is disclosed in U.S. Pat. No. 2,430,674 to C. A. Hampel. The use of sodium hypochlorite as a preservative is not suggested.
U.S. Pat. No. 3,978,235, to Schiro, discloses the use of sodium hypochlorite in mixture with an alkali earth metal phosphate for preserving produce and cut flowers.
The use of Milton's Solution having a sodium hypochlorite concentration from 50 to 100 ppm and a sodium chloride concentration from 825 to 1650 ppm for anti-fungal treatment of kola nuts is described in Olunloyo (1979) Niger. Jour. Agric. Sci. 1:51-59.
Additional United States patents show various preservative compositions and methods of preserving or maintaining the freshness and color of produce including fruit and vegetables. Such patents include: Hall-U.S. Pat. No. 2,082,573; Sharma-U.S. Pat. No. 2,092,090; Kalmar-U.S. Pat. No. 2,374,210; Matarozzo-U.S. Pat. No. 2,420,322; Wilson-U.S. Pat. No. 2,441,305; Gericke-U.S. Pat. No. 2,503,663; Pryor-U.S. Pat. No. 2,522,535; and Bedrosian-U.S. Pat. No. 3,102,777. Again, while most of these prior art patents show a preservative product or process, they do not show the use of a composition which will react with the produce in an efficient manner having no deleterious effects on either taste, smell or appearance.